Stark Spectroscopy of Absorption and Emission of Indoline Sensitizers: A Correlation with the Performance of Photovoltaic Cells

Ohta, Nobuhiro; Awasthi, Kamlesh; Okoshi, Kenji; Manseki, Kazuhiro; Miura, Hidetoshi; Inoue, Yukiko; Nakamura, Kôsuke; Kono, Hirohiko; Diau, Eric Wei Guang

doi:10.1021/acs.jpcc.6b08531

Cited by 28 publications

(17 citation statements)

References 43 publications

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“…In most reports, the absorption coefficient α that used to fit the measured EM spectrum in device were independently determined from the thin film optical absorption 51–53 . However, due to optical interference effect, the absorption in thin film can be significantly different from the absorption of the active layer sandwiched in a multilayer structured device.…”

Section: Resultsmentioning

confidence: 99%

A generalized Stark effect electromodulation model for extracting excitonic properties in organic semiconductors

et al. 2019

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Electromodulation (EM) spectroscopy, a powerful technique to monitor the changes in polarizability p and dipole moment u of materials upon photo-excitation, can bring direct insight into the excitonic properties of materials. However, extracting Δp and Δu from the electromodulation spectrum relies on fitting with optical absorption of the materials where optical effect in different device geometries might introduce large variation in the extracted values. Here, we demonstrate a systematic electromodulation study with various fitting approaches in both commonly adopted reflection and transmission device architectures. Strikingly, we have found that the previously ascribed continuum state threshold from the deviation between the measured and fitting results is questionable. Such deviation is found to be caused by the overlooked optical interference and electrorefraction effect. A generalized electromodulation model is proposed to incorporate the two effects, and the extracted Δp and Δu have excellent consistency in both reflection and transmission modes in all organic film thicknesses.

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Section: Resultsmentioning

confidence: 99%

A generalized Stark effect electromodulation model for extracting excitonic properties in organic semiconductors

et al. 2019

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“…30 Thus, metal-free organic sensitizers have drawn greater attention over metal-based organic sensitizers due to their low toxicity, high structural flexibility, environment friendly nature, high MECs, and facile synthesis. 31,32 It is to be noted that previously, several chromophores such as indoline, 33,34 coumarin, 35,36 phenothiazine, 37,38 carbazole, 39,40 triarylamine, 41,42 tetrathiafulvalene, 43,44 etc were used in the assembly of organic sensitizers. Better structure-property relationship elucidation will encourage the better use of these dyes in DSSCs.…”

Section: Discussionmentioning

confidence: 99%

Recent developments in metal‐free organic sensitizers derived from carbazole, triphenylamine, and phenothiazine for dye‐sensitized solar cells

et al. 2021

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Summary In the present context of increasing population, renewable and sustainable energy alternatives are very much essential to satisfy the necessities of the world. To satisfy this growing demand, scientists are prioritizing the production of cost‐effective and high‐performance clean energy appliances. Dye‐sensitized solar cells (DSSCs) are one such material that is at the forefront of modern solar cell technologies. Being one of the main components of DSSCs, metal‐free organic dyes play a crucial role in light processing and electron injection. In recent times, carbazole (CZ)‐, triphenylamine (TPA)‐, and phenothiazine (PTZ)‐based derivatives have been identified as suitable alternatives to Ru(II) polypyridyl complexes because they are easy to synthesize and exhibit excellent thermal and electronic properties. This review focuses largely on the latest developments in the use of monoanchored and multianchored CZ, TPA, and PTZ scaffolds for DSSC applications and focuses especially on the correlation between molecular design and photovoltaic performance. The physical properties of devices can be adjusted through the sensitizer's strategic design that helps to improve the performance of the devices. We tabulated the photovoltaic parameters corresponding to all dyes presented in this review. Also, applications of additives are presented after the systematic review on CZ‐, TPA‐, and PTZ‐based dyes.

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“…Electrons injected into TiO 2 emanate an electric field that significantly influences the absorption spectra of surface anchored sensitizers. , The electro-absorption features provide a useful means to quantify the impact of electric fields on sensitizer orientation, ion migration (termed screening), and interfacial electron transfer. − The feature has also been utilized to quantify the field strength of rigid-rod sensitizers set at variable distances from the TiO 2 surface . A simplified basis for the electro-absorption is shown in Figure a.…”

Section: Discussion and Perspectivesmentioning

confidence: 99%

Perspectives on Dye Sensitization of Nanocrystalline Mesoporous Thin Films

Sampaio

Schneider

et al. 2020

J. Am. Chem. Soc.

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Recent advances in our mechanistic understanding of dye-sensitized electron transfer reactions occurring at metal oxide interfaces are described. These advances were enabled by the advent of mesoporous thin films, comprised of anatase TiO 2 nanocrystallites, that are amenable to spectroscopic and electrochemical characterization in unprecedented molecular-level detail. The metal-to-ligand charge transfer (MLCT) excited states of Ru polypyridyl compounds serve as the dye sensitizers. Excited-state injection often occurs on ultrafast time scales with yields that can be tuned from unity to near zero through modification of the sensitizer or the electrolyte composition. Transport of the injected electron and the oxidized sensitizer (hole hopping) are both operative in the composite mechanism for charge recombination between the injected electron and the oxidized sensitizer. Sensitizers that contain a pendant electron donor, as well as core/shell SnO 2 /TiO 2 nanostructures, often prolong the lifetime of the injected electron and provide fundamental insights into adiabatic and nonadiabatic electron transfer mechanisms. Regeneration of the oxidized sensitizer by iodide is enhanced through halogen bonding, orbital pathways, and ion pairing. A substantial ∼10 MV cm −1 electric field is created by electron injection into TiO 2 nanocrystallites that induces ion migration, reports on the sensitizer dipole orientation, and (in some cases) reorients or flips the sensitizer. Dye-sensitized conductive oxides also promote long-lived charge separation with bias dependent kinetics that provide insights into the reorganization energies associated with electron and proton-coupled electron transfer in the electric double layer.

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Stark Spectroscopy of Absorption and Emission of Indoline Sensitizers: A Correlation with the Performance of Photovoltaic Cells

Cited by 28 publications

References 43 publications

A generalized Stark effect electromodulation model for extracting excitonic properties in organic semiconductors

A generalized Stark effect electromodulation model for extracting excitonic properties in organic semiconductors

Recent developments in metal‐free organic sensitizers derived from carbazole, triphenylamine, and phenothiazine for dye‐sensitized solar cells

Perspectives on Dye Sensitization of Nanocrystalline Mesoporous Thin Films

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